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SubjectRe: Drivers that potentially leave state as TASK_{UN}INTERRUPTIBLE
You can ran into problems using schedule_timeout() in a block device request 
function under 2.4.

This can be demonstrated by starting some I/O intensive tasks to your block
device and running sync in another task. Eventually the block layer will
lock up.

This can be fixed by creating a kernel thread per flash device to handle
the I/O requests. Within the thread schedule_timeout() works fine. This
solution also works under 2.2 and 2.0.38

dwmw2@infradead.org (David Woodhouse) said:

> moz@compsoc.man.ac.uk said:
> > So it seems to be a bug at least in terms of timing. Unfortunately I
> > only got about 4 replies to the patches that touched 20+ drivers. I
> > suppose I should just hassle maintainers until they fix it or tell me
> > where I've gone wrong ...
>
> Actually, I was quite happy calling schedule_timeout in the flash drivers
> without changing current->state. I'm waiting to something to happen, and
> just to be considerate, I'm asking to be put to sleep for the 'expected'
> amount of time for whatever's happening. If there's other stuff on the run
> queue, it won't return immediately, will it? If there isn't other stuff on
> the run queue, I'll just busy wait till the flash chip's finished.
>
> Otherwise, it would be TASK_UNINTERRUPTIBLE.

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